1. Field of the Invention
The present invention relates to an electrical commutator for electric motors and the like.
2. Description of the Prior Art
Electrical commutators of the type used in electric motors and the like typically comprise a plurality of commutator segments which are arranged to form a tubular cylindrical sleeve. These commutator segments are constructed of an electrically conductive material, usually copper, and which are separated from each other by an electrical insulating material. This electrical insulating material can comprise an air space, mica, phenolic resin as well as other substances.
In order to connect the commutator to the electrical windings for the motor, a winding tang is provided at one end of each commutator segment. These winding tangs typically extend radially outwardly from the commutator segments and are bent backward over the commutator sleeve so that a portion of each tang overlies the commutator sleeve.
There are two commonly used methods for constructing commutators. In one method, a plurality of individual commutator segments are positioned within the interior of a cylindrical mold. Each commutator segment typically includes an anchoring portion which protrudes radially inwardly from the commutator segment while insulating means, such as a mica layer, may also be positioned between adjacent commutator segments. Thereafter, the anchoring portions of the commutator segments are encapsulated with an electrical insulating material which, upon setting, secures the commutator segments together.
In a second and less expensive type of commutator, as shown in FIG. 1, the commutator is formed by bending a strip 10 of conductive material into a cylindrical sleeve. The strip 10 of conductive material includes a plurality of spaced apart tangs 14 which protrude outwardly from one side of the strip. Consequently, once the sleeve is formed, the tangs 14 protrude outwardly from one axial end of the sleeve. Anchoring portions extend inwardly from the interior of the sleeve and these anchoring portions are encapsulated with a moldable insulating material 16 which, upon setting, secures the anchoring portions together.
Thereafter, an axially extending slot 20 is machined in the commutator between each adjacent pair of winding tangs 14 so that the slots 20 extend entirely through the conductive strip 10. In doing so, the slots 20 form a plurality of commutator segments 22 which are electrically insulated from each other by the encapsulating material 16 as well as the air space which is formed by the slot 20. Furthermore, as shown in FIG. 1, the slot 20 extends into the space 24 between adjacent tangs 14 but terminates short of the edge of the encapsulating material 16 thus forming a fluid dam 26. This dam 26 prevents the trickle resin used to adhere the electrical commutator wires together from entering into the slot 20. Otherwise, these slots 20 would have to be undercut or remachined to remove such resin.
A primary disadvantage of the previously known shell-type commutators is that the wiring tangs 14 are unsupported by anchoring portions encapsulated in the molding material 26. Consequently, under high speed rotation of the commutator, the wiring tangs 14 tend to deflect which can damage not only the commutator, but also the electrical windings for the motor.